mineral

Botryoidal chalcedony (likely chert/flint nodule)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Tan-brown, dull to waxy luster, rounded botryoidal surface with white crystalline specks; hardness about 6.5–7 Mohs, no cleavage, conchoidal fracture, and specific gravity near 2.6. The major cracks may reflect natural breakage or weathering.

Identified September 3, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited microcrystalline quartz in cavities or around a nucleus, commonly forming nodules in limestone or volcanic rocks. Most examples are Phanerozoic, though chalcedony forms across many geological ages.

Uses & applications

Used for carvings, cabochons, lapidary pieces, abrasives, and decorative specimens; attractive material may be sold as jasper or agate. Ordinary nodules have little industrial value.

Geological facts

Botryoidal means grape-like rounded growths. The tan color commonly comes from iron-oxide staining or included clay, while the white patches may be quartz druse or weathered matrix.

Field identification & locations

Look for waxy luster, very fine texture, conchoidal fracture, and inability to scratch it with a steel knife; it should scratch glass. Common localities include limestone regions and volcanic terrains worldwide, especially Brazil, Mexico, India, and the western United States.